1. Field of the Invention
The present invention relates to methods for automatically generating filled embroidery patterns in a computer aided design system, and more particularly to an improved method for automatically generating chain stitches in a computer aided design system.
2. Description of the Prior Art
Computer aided design systems for controlling embroidery machines are well known in the art. Such systems allow the user to select embroidery patterns to be stitched either through a stored series of designs or creation of original designs, such as described in our copending United States patent application entitled "Method for Creating Self-Generating Embroidery Pattern" filed Oct. 4, 1993, and bearing U.S. Ser. No. 08/131142, U.S. Pat. No. 5,430,658 and our previously issued U.S. Pat. No. 5,343,401, entitled "Embroidery Design System". In such prior art systems, embroidery patterns may typically be generated in an outline form of a particular shape such as a letter or an animal, or may be filled in with stitches. It is also known in the art to be able to modify the embroidery design programs used in such computer aided design systems so that the user may independently vary and modify a large variety of characteristics of an existing embroidery design program including, such as described in our previously issued U.S. Pat. No. 5,270,939.
In addition, chenille type embroidery machines capable of providing chenille type stitching, which produces a towel like effect in the embroidery pattern, are also well known, such as disclosed, by way of example, in U.S. Pat. No. 5,056,444. A typical conventional chenille type embroidery machine is manufactured by Tajima Industries Ltd. of Japan. As noted in U.S. Pat. No. 5,056,444, which describes a prior art chenille type embroidery machine, chenille type embroidery machines provide a fuzzy appearance of a pattern, for example, such as on an athletic award or letter, with the fuzzy appearance being formed by the use of a hooked needle which, in combination with a looper, which wraps thread around the needle (as illustrated in FIGS. 1A-1E), pulls a thread through a piece of material. Such a stitch is known as a "moss" stitch and is performed by the looper looping thread over the hook of the needle below the material to be embroidered. The needle then pulls the looped thread through and above the material. Another device known as the X/Y drive then pulls the material away from the raised needle causing the looped thread to slip off the hook. The needle again penetrates the material and the process is repeated, resulting in a fuzzy patterned item.
By reversing the hook of the needle so that the looped thread remains on the hook after the X/Y movement of the material, a chain stitch can be formed. In such an instance, the X/Y drive pulls the material and the thread as in the above described prior art moss stitch procedure, but now the thread remains on the hook as the needle repenetrates the material and a linked chain stitch is formed, such as illustrated in FIGS. 2A-2E. Chain stitching is generally used to follow the perimeter of a shape. Chenille stitching may be used to create a cross hatch or lattice chenille, such as illustrated in FIG. 3, or a spiral type chenille. In a lattice chenille, the pattern that is created by the loop stitch in order to fill a shape, with the stitching starting at one point in the shape and moving in straight lines diagonally covering the area, whereas in a spiral type chenille, in order to fill the shape the stitching is performed in a spiral fashion causing the embroidery machine to place stitches at many varying angles to provide a random/hand-done appearance.
Chenille stitching in the past was generally performed by hand which is a very tedious, time consuming task, and did not utilize the advantages of a computer aided design system which could allow the operator to make decisions on how the coverage would take place. Prior to applicants' invention, spiral coverage for chenille stitches was not automatically generated, but, rather, was accomplished either by hand or manually entered in the computer. Moreover, where the pattern was a complex polygon, there were difficulties in the prior art in trying to place chain stitching around a complex polygon. Thus, applicants are not aware of any efficient prior art computer aided design systems for generating filled embroidery patterns which enable chenille filled embroidery patterns, or chain stitches, to be automatically generated and this is so despite the wide spread use of computer aided design systems for controlling embroidery machines.